コンクリートの打込み方法がコールドジョイントの発生およびコンクリートの中性化・鉄筋の発錆に及ぼす影響(<特集>建設材料)

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It is important to place concrete continuously for construction being joint-less. However, in case placing is discontinued for some reasons, some defects such as cold joints should remain. At the first stage in this study, effects of placing conditions on continuity of concrete were investigated. The flexural and compressive strength at joint between placing layers was almost the same as that of joint-less concrete when upper layer concrete was placed over lower layer immediately after the lower layer being revibrated and softened to wet until the initial setting. This result was the same as what is recommended in J.S.C.E. Specification 1974. This principle was deleted from the Specification 1986 onward, because ready mixed concrete had been common and continuously placed by concrete pump. At the next stage, effects of placing time interval on carbonation and corrosion were evaluated by some accelerated tests on specimens compacted without revibration before placing upper layer concrete. This study shows that the longer the placing time interval, the faster the carbonation velocity factor becomes and the earlier the corrosion starts. When the placing time interval is required by some accidents, lower layer concrete should be revibratd in order not to make any defects; otherwise it would be necessary that carbonation velocity and margin of cover concrete depth recommended in the Specification January 2000 should be increased. On the other hand, some type of monitoring specimen would be necessary to maintain the durability of RC structures as there are uncertainties, such as effective use of recycled aggregate, new type of cement such as eco-cement, and change of environment due to industrialization of neighboring countries. It is also clarified that a specimen which is tested in this accelerated test can probably indicate environmental conditions when the specimen is applied to monitor.
社団法人日本材料学会の論文
2001-08-15

コンクリートの打込み方法がコールドジョイントの発生およびコンクリートの中性化・鉄筋の発錆に及ぼす影響(<特集>建設材料)

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